Detector facilities of this kind are used in computed tomography systems in particular. The individual detectors concerned are generally analog components (the individual detectors are therefore also frequently referred to as “analog frontends”), which comprise the actual detector elements, which as individual detector pixels convert the incoming X-ray radiation into electrical signals as measurement data, and at least one highly integrated analog-digital converter (ADC) and a multiplexer connected upstream of the ADC, which transfers the analog signals of the detector elements or pixels to the shared ADC. How many such individual detectors a detector facility has will depend firstly on the total number of detector elements or pixels of the detector and secondly on the number of pixels or detector elements per individual detector.
Thus, for example, there are “smaller” individual detectors comprising only 16 channels for 16 individual pixels and a shared multiplexer with an ADC connected downstream. Equally, there are also individual detectors with 64 channels or more. For a detector facility with only 64 or 128 pixels, it would therefore basically suffice to use just one or two individual detectors with 64 channels each. As a rule, however, a plurality of individual detectors is needed.
The measurement data digitalized by the ADCs is sent by the individual detectors to the detector controller, which serves not only to accept the measurement data or raw data for image reconstruction but also to control the individual detectors, i.e. to transmit corresponding control signals to the latter in order, for example, to read out the measurement data in a synchronized manner, etc. The electronics of the detector controller normally operate digitally, which is why the detector controller is usually also referred to as a “digital backend”.
In order to provide the large number of pixels (customary computed tomography systems have around 50,000 pixels or even more) and the electronics for controlling the individual detectors and for transferring the relatively large quantities of data, i.e. the recorded projection data or raw data, these detector facilities need a lot of power. Depending on the detector type and number of individual detectors, a power of up to 400 watts or in individual cases even more is currently needed. The bulk of the power needed is accounted for by the individual analog detectors. Thus, these need, at a rough estimate, approx. 95% of the total power of the detector facility. As the number of pixels (and thus usually also of individual detectors) is constantly rising—computed tomography systems with more than 100,000 pixels are currently in the planning stage—it can be assumed that in future the power requirements will be even higher.
Irrespective of the current use of the medical imaging system or computed tomography system, previously the maximum power for the complete detector electronics system has always been consumed. In clinics and radiological practices, however, it can frequently arise that a computed tomography system will be operated for a prolonged period without any direct patient examination, i.e. without raw data for images currently being acquired. This period may amount to just a few minutes, for example between two scans of a patient, if the latter has to be repositioned, for example, or if other organs are to be recorded or a contrast agent has first to be administered. Between different patients, however, this period may also extend from a few hours to half a day or even overnight. In order to reduce unnecessary energy consumption during prolonged waiting periods, there has previously only been the option of shutting down the entire computed tomography system, which in turn, however, comes at the expense of the time that is needed in order to return the device to operating mode again. Shutting down the entire system is therefore not possible in many cases, in particular where it is clear that the next patient examination will take place in a foreseeable period, but also possibly overnight when e.g. emergency cases are likely.